Re: OUTER joins

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От Bruce Momjian
Тема Re: OUTER joins
Дата
Msg-id 199903070325.WAA10357@candle.pha.pa.us
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Ответ на Re: OUTER joins  ("Thomas G. Lockhart" <lockhart@alumni.caltech.edu>)
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> (back from a short vacation...)
> 
> > How do you propose doing outer joins in non-mergejoin situations?
> > Mergejoins can only be used currently in equal joins.
> 
> Hadn't thought about it, other than figuring that implementing the
> equi-join first was a good start. There is a class of outer join syntax
> (the USING clause) which is implicitly an equi-join...

Not that easy.  You don't automatically get a mergejoin from an
equijoin.  I will have to force outer's to be either mergejoins, or
inners of non-merge joins.  Can you add code to non-merge joins in the
executor to throw out a null row if it does not find an inner match for
the outer row, and I will handle the optimizer so it doesn't throw a
non-conforming plan to the executor.

--  Bruce Momjian                        |  http://www.op.net/~candle maillist@candle.pha.pa.us            |  (610)
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